Angioplasty and stenting of blood vessels or other body lumens are commonly performed today. Angioplasty is often performed by expanding a balloon in a vessel in order to reduce or eliminate plaque or other blockages. In many cases, a stent is also implanted in the vessel in order to further ensure a positive clinical result. A stent is an implantable scaffold that is typically delivered percutaneously and deployed in a vein, artery, or other tubular body organ for treating an occlusion, stenosis, aneurysm, collapse, dissection, or weakened, diseased, or abnormally dilated vessel or vessel wall. The stent is radially expanded in situ, thereby expanding and/or supporting the vessel wall or body organ wall. In particular, stents are quite commonly implanted in the coronary, cardiac, pulmonary, neurovascular, peripheral vascular, renal, gastrointestinal and reproductive systems. Stents have also been successfully used to reinforce other body parts, such as the urinary tract, the bile duct, the esophagus, the tracheobronchial tree and the brain.
Stents may improve angioplasty results by preventing elastic recoil and remodeling of the vessel wall. Stents also can be used to treat dissections in blood vessel walls that are caused by balloon angioplasty. In this situation, the stent is used to appose dissected intimal flaps of tissue which otherwise would extend into and block a vessel.
Conventional stents have also been used to treat more complex vascular problems, such as lesions at or near bifurcation points in the vascular system. A bifurcation is where a secondary artery (sometimes referred to as a side branch or daughter vessel) branches out of a typically larger vessel (sometimes referred to as the main branch or mother vessel). Stenting of bifurcations can present may challenges. For example, a stent that traverses the ostium of the side branch may obstruct blood flow into the side branch. Moreover, the struts in a stent may also block the side branch, limiting or preventing access to the side branch by another diagnostic or therapeutic device such as another catheter. This phenomenon is commonly referred to as “stent jailing.” In still other situations, inflation of balloons and expansion of stents in a bifurcation can result in undesirable plaque shifting, which is sometimes referred to as “snow plowing.” Other challenges with treatment of a bifurcated vessel can be the result of vessel spasm, dissection, thrombosis, etc.
More recently stents and balloons have also been used to elute drugs locally to the treatment site. Drugs such as rapamycin, everolimus, biolimus A9 and other analogs of rapamycin, as well as paclitaxel are promising in reducing restenosis rates, yet many of the aforementioned challenges of treating a bifurcation still exist.
It would therefore be desirable to provide improved medical devices and methods for treating bifurcated vessels. It would also be desirable to provide improved medical devices and methods that are easier to use, safer, more reliable, and that provide a better clinical outcome compared with currently available medical devices.
Therefore, given the challenges of current stent technology, a need exists for improved stent delivery systems and methods, particularly for treating bifurcated vessels. At least some of these objectives will be met by the present invention.